fork oil mixing


8 replies to this topic
  • white line

Posted July 16, 2007 - 09:32 AM

#1

its time to change oil in my forks. i have a new qt of belray 20wt and a new qt of belray 5wt. if i put them together would they mix and stay mixed to make 12.5wt. thanks

  • Denn10

Posted July 16, 2007 - 10:09 AM

#2

you prolly dont want oil that thick id just go get some fresh oil in the weight you want

  • cleonard

Posted July 16, 2007 - 10:44 AM

#3

The question is why.

I'm currently running ATF in my 93. It is around 15 to 17wt. I need the proper springs for my weight, but that is not in the budget right now. As I have been riding more aggressively, I needed some more resistance to bottoming. The thicker oil helped a lot, but there was a price. I get a lot more little stuff transmitted to my hands. The plushness is not there any more. I live with this because I would much rather not crash from a big impact.

New springs and lighter fluid are in my future though.

  • Denn10

Posted July 16, 2007 - 12:46 PM

#4

why would u use automatic tranny fluid instead of just getting fork oil?

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  • martinfan30

Posted July 17, 2007 - 02:28 PM

#5

i remember an article in some mag(cant remember.)awhile back saying you can mix oils. i know with eng. oil you can mix grades, just not brands and/or synth.,, synth/blend, conventional. at least this is what ive been taught.

  • cleonard

Posted July 17, 2007 - 03:09 PM

#6

why would u use automatic tranny fluid instead of just getting fork oil?


I wanted to try the thicker oil and I had it in my garage. It was just an experiment, and since I liked the results I left it in there. I had actually purchased some Honda SS7 and I'll put that back in there when I get some higher rate springs. There is no problem with using ATF. It is compatible with the materials in the forks. In the 70's and 80's ATF was recommended for the forks in several bikes including my old Honda XL's.

  • Jon-D

Posted July 17, 2007 - 07:32 PM

#7

I use the Mobile 1 ATF in my KTM forks and they work great. Cheaper then fork fluid and work just as well or better then some brands. Most ATFs are 7.5W (the Mobile 1 is) so you want to valve for that fluid if you decide to use it. In the XR (conventional forks) I run a 15W oil with no pressure in the forks and it seems to do fine for me. I say try the 12.5W mix and see if you like it.

Cleonard - what brand of ATF are you using that is 15-17 Wt? I'd like to give it a try next time I change out my fork fluid.

  • cleonard

Posted July 20, 2007 - 03:52 PM

#8

Cleonard - what brand of ATF are you using that is 15-17 Wt? I'd like to give it a try next time I change out my fork fluid.


Well once I looked up the characteristics for Dextron III and the numbers seemed to convert to on the high end of 15 and the low end of 20. That was the generic spec, not the spec on a particular brand.

It really seems thicker than the 5 wt SS7 that I had before. The fork action is much different. It is much harsher over the little choppy stuff, but acts better in the bottoming resistance of the last few inches of travel. I think that I am using Castrol.

From the Mobil website

Viscosity, ASTM D 445
cSt @ 40º C 34
cSt @ 100º C 7.6
Viscosity Index, ASTM D 2270 199


From those numbers it is closer to 20 wt. The range for 20 wt is 5.6 - 9.3 cSt at 100º C. I wiuld call it 20wt because 7.6 is almost smack in the middle of that range. I just looked it up and the Castrol that I used is 7.1.

Everyone labels the oils different. For example Maxima gives these specs for thier fork oil

5W 4.41
10W 7.72
15W 8.49
20W 11.28


On this scale the ATF is about the same as 10W Maxima fork oil.

The Honda SS7 fluid is 4.1 at 100C.

  • Jon-D

Posted July 20, 2007 - 05:07 PM

#9

Well once I looked up the characteristics for Dextron III and the numbers seemed to convert to on the high end of 15 and the low end of 20. That was the generic spec, not the spec on a particular brand.

It really seems thicker than the 5 wt SS7 that I had before. The fork action is much different. It is much harsher over the little choppy stuff, but acts better in the bottoming resistance of the last few inches of travel. I think that I am using Castrol.

From the Mobil website


From those numbers it is closer to 20 wt. The range for 20 wt is 5.6 - 9.3 cSt at 100º C. I wiuld call it 20wt because 7.6 is almost smack in the middle of that range. I just looked it up and the Castrol that I used is 7.1.

Everyone labels the oils different. For example Maxima gives these specs for thier fork oil



On this scale the ATF is about the same as 10W Maxima fork oil.

The Honda SS7 fluid is 4.1 at 100C.



Thanks for the info Cleonard. Now if I can only talk you into fixing my XR for me...





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